The present invention relates to large copy projectors and, more particularly, to visual transparency projectors of the type in which a large transparency to be marked and/or observed by an operator is imaged on a viewing screen for display to an audience.
Visual transparency projectors of the prior art, usually known as overhead projectors, have been characterized by bulky hardware that obtrudes between the audience and the viewing screen and causes the operator to assume an unnatural posture in an effort not to obtrude between the audience and the viewing screen.
The primary object of the present invention is the provision of a visual transparency projector characterized by a short throw, oblique incidence catadioptric optical system, capable of enabling (1) a viewing screen and (2) the projector with its operator to be seen by an audience in side-by-side relation with minimal keystoning. Specifically, the projector comprises a Fresnel lens for supporting the visual transparency, a mirror extending obliquely downwardly below the Fresnel lens from its rearward edge toward its forward edge, a lamp above the Fresnel lens at one of its forward corners, and an objective catadioptric reflector below the Fresnel lens at the other of its forward corners, the catadioptric reflector having an extremely wide field angle and a pair of semi-field conjugate surfaces, both on the same side of the catadioptric reflector, one of which is disposed at the visual transparency and the other of which is disposed at the viewing screen.
Other objects will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the apparatus, together with its components and their interrelationships, which are exemplified in the present disclosure, the scope of which will be indicated in the appended claims.